Marine Interpretation Message
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
AGNT40 KWNM 270121
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
921 PM EDT TUE JUL 26 2016

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.

NO MAJOR CHANGES TO THE ONGOING OPC FCST APPEAR NEEDED FOR THE EVE
UPDATE. WE WILL ONLY TWEAK GRIDS SLIGHTLY TO FIT CONDITIONS NOTED
JUST PRIOR TO FCST ISSUANCE AND ALSO TWEAK THEM SLIGHTLY TO FIT
NEARBY COASTAL WTRS AND TAFB FCSTS A LITTLE BETTER. THE 00Z PRELIM
SFC ANALYSIS SHOWS A WEAK COLD FRONT MOVG FROM NT1 INTO NRN NT2
WTRS...WITH A WEAK LOW PRES TROF TRAILING THE FRONT JUST OFF THE
NEW ENGLAND COAST. THE 18Z GFS IS CONSISTENT OVR THE SHORT TERM
WITH THE 12Z CYCLE. THE FRONT IS FCST TO STALL OVR NRN AND CENTRAL
NT2 WTRS WED AND WED NITE. THE LATEST RADAR...SATELLITE...AND
LIGHTNING DENSITY IMAGERY INDICATES WEAKENING SCTD TSTMS MOVG E-SE
OFF THE COAST JUST N OF CAPE HAT...WITH ADTL SCTD TSTMS WELL OFF
THE MID ATLC COAST...OVR OFF ZONE ANZ910. THE LATEST SREF TSTMS
GUIDANCE KEEPS THE HIGHEST CHANCES FOR TSTMS OVR NRN AND CENTRAL
NT2 WTRS THRU WED...AND THIS IS REFLECTED IN THE ONGOING FCST.

SEAS...SEA HEIGHTS RANGED FROM 1 TO 2 FT OVR THE GULF OF MAINE AND
FAR SW NT2 WTRS...TO 6 FT WELL OFF THE MID ATLC COAST OR NR ZONE
ANZ910 PER THE LATEST OBS AND ALTIMETER DATA. LITTLE CHANGE
APPEARS NECESSARY FOR THE EVE UPDATE. WE WILL MAKE A FEW MINOR
ADJUSTMENTS TO FIT THE PREV GRIDS WITH THE LATEST CONDITIONS AND
WITH NEARBY FCSTS...BUT OVERALL MAKE NO MAJOR CHANGE FOR THE EVE
UPDATE.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE 14Z AND 15Z ASCAT OVERPASSES RETURNED HIGHEST OFFSHORE WINDS
TO 20 KT ACROSS THE GULF STREAM E OF 73W. 12Z MODELS WERE WELL
INITIALIZED WITH THESE WINDS THIS MORNING...AND DO NOT OFFER
MAJOR DIFFERENCES ACROSS THE W ATLC FOR THE NEXT FEW DAYS. A
WEAK COLD FRONT CONTINUES TO SLOWLY APPROACH THE NEW ENGLAND AND
NRN MID ATLC COASTS AND HAS NEARLY REACHED LONG ISLAND THIS
AFTERNOON. AT 18Z A PREFRONTAL TROUGH ALSO STRETCHED SW ACROSS
THE NRN NT2 WATERS TO NEAR CAPE CHARLES. THE 20 KT WINDS SEEN IN
THIS MORNINGS ASCAT WERE S OF THIS FEATURE. 12Z MODELS ARE
CONSISTENT IN SHOWING THE WEAK COLD FRONT WILL REACH THE NRN MID
ATLC WATERS WED AND PERSIST INTO EARLY THU...BEFORE WASHING OUT
THU NIGHT. GFS HAS BEEN MORE EMPHATIC ABOUT MAINTAINING THE WEAK
QUASI STATIONARY BOUNDARY. FOR WIND GRIDS WILL CONTINUE TO USE
THE 12Z GFS THROUGH WED NIGHT. LATER IN THE WEEK THE GFS HAS
BEEN CONSISTENTLY MORE PROGRESSIVE THAN THE ECMWF/UKMET/CMC WITH
A DEVELOPING SURFACE LOW TO MOVE OFF THE NRN MID ATLC COAST AND
THROUGH THE SRN NT1 WATERS LATE FRI INTO SAT. 12Z GEFS OFFERS
BETTER SUPPORT FOR THE SLOWER ECMWF/UKMET...AND ALSO SUGGESTS
THAT THE GFS MAY BE TOO WEAK WITH LOW. VERSUS ITS 00Z RUN THE
12Z ECMWF WAS SLIGHTLY STRONGER AND MORE IN LINE WITH ITS 12Z
RUN YESTERDAY. 12Z UKMET ALSO TRENDED STRONGER. BASED ON THIS
PLAN AM FAVORING THE 12Z ECMWF THU THROUGH THE WEEKEND...AND
LIKE WAS DONE PREVIOUSLY WILL ADJUST THESE S TO SW WINDS HIGHER
BY ABOUT 10 PERCENT FRI NIGHT INTO SAT OVER THE OUTER NT2 WATERS
N OF HATTERAS CANYON ACROSS THE GULF STREAM. THIS WILL RESULT IN
INTRODUCING SOME 30 KT WINDS FOR A BRIEF PERIOD ACROSS ANZ920
AND ANZ910 ZONES. 12Z ECMWF AND 12Z UKMET CONTINUE IN GOOD
AGREEMENT THAT COLD FRONT ASSOCIATED WITH FRI/SAT LOW WILL STALL
NEAR THE DELMARVA SAT NIGHT...AND REMAIN NEARLY STATIONARY
ACROSS THE NRN NT2 WATERS SUN/SUN NIGHT AS WEAK LOW PRES MOVES E
ALONG THE FRONT. 12Z MODELS ARE MOSTLY CONSISTENT THAT WINDS TO
20 OR 25 KT S OF THE FRONT SHOULD PERSIST THROUGH SUN NIGHT.

SEAS...THE 12Z WAVEWATCH III AND 12Z ECMWF WAM ARE ABOUT 1 FT
TOO HIGH WITH WAVE HEIGHTS ACROSS THE NT1 WATERS BUT ELSEWHERE
ARE WELL INITIALIZED THIS AFTERNOON...AND ARE IN GOOD AGREEEMENT
THROUGH THU. TO BE CONSISTENT WITH WINDS WILL POPULATE WITH THE
12Z WW3 THROUGH WED NIGHT...THEN SWITCH TO THE 12Z ECMWF WAM THU
THROUGH SUN NIGHT.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER MILLS/CLARK. OCEAN PREDICTION CENTER.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.